Limaco ULM-3D Series, Руководство по эксплуатации и установке

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Nozzle height
H
is measured along its inner surface from the flange to the lower
edge of the hole. The maximum permissible nozzle height depends on its diameter.
The larger the diameter, the higher the permissible nozzle.
Using a nozzle exceeding recommended size may cause spurious re-reflections and
hinder the measurement process. The opening in the roof under the nozzle shall be
not less than the inner nozzle diameter. The inner nozzle surface shall not contain
irregularities larger than 3 mm. Spurious reflections from irregularities inside the
nozzle can lead to poor measurement accuracy and stability.
In case of rectangular nozzles, the height of nozzle including roof thickness together
with internal structures adjacent to the roof (stiffeners, etc.) shall not exceed the
values given below, where the size of narrow rectangle side is recorded instead of
nozzle diameter.
The height of mounting nozzle shall not exceed its diameter:
D H
=
.
Do not use nozzles higher than 250 mm for the measurement of bulk products.
4.5 Measurement beam coverage
ULM-3D-5 device has five measuring channels Fig. 3.9. We have five independent
measuring beams on the product surface. The width of beam pattern is 2 degrees.
The coverage of measuring beams is determined independently in two mutually
perpendicular planes. The value of angular sector for each plane is equal to the sum
of beam tilt angles of two channels lying in this plane. For each device, for each
measuring channel, the value of beam tilt angle is given in the device data sheet.
The maximum beam tilt angle is 25 degrees. Tilt angles are established during man-
ufacturing in accordance with the pre-order.
4.6 Blind spot
The level transmitter has a so-called "blind spot". This is the area near the level
transmitter aerial, where measurement is difficult or impossible. The "blind spot" is
shown in Fig. 4.9, it can be divided into three regions. The nearest region (left in the
figure) is where the measurement is impossible. Intermediate region of unstable
measurements, the device can determine the distance with low accuracy, there may
be spikes in readings. The far region of the "blind spot" is where the measurements
are stable, but rated accuracy is not achieved. The size of the "blind spot" regions
depends on the product's reflectivity and the presence of tank structures that fall into
the beam of level transmitter. The "blind spot" does not exceed 600 mm subject to
the observation of rules for device installation on the tank.
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RE_ULM3DX_18_02_20